package leetcode; /**
 * description:
 * author:张腾
 * date:2021-07-16
 */

/**
 * 给你一个由'1'（陆地）和 '0'（水）组成的的二维网格，请你计算网格中岛屿的数量。
 *
 * 岛屿总是被水包围，并且每座岛屿只能由水平方向和/或竖直方向上相邻的陆地连接形成。
 *
 * 此外，你可以假设该网格的四条边均被水包围。
 *
 输入：grid = [
 ["1","1","0","0","0"],
 ["1","1","0","0","0"],
 ["0","0","1","0","0"],
 ["0","0","0","1","1"]
 ]
 输出：3
 */
public class leetcode200 {
    public int numIslands(char[][] grid) {
        int count = 0;
        for (int i = 0; i < grid.length; i++) {
            for (int j = 0; j < grid[0].length; j++) {
                if (grid[i][j]=='1') {
                    dfs(grid,i,j);
                    count++;
                }
            }
        }
        return count;
    }

    private void dfs(char[][] grid, int i, int j) {
        if (i<0 || i>=grid.length || j<0 || j>=grid[0].length || grid[i][j]=='0') return;

        grid[i][j] ='0';
        dfs(grid,i+1,j);
        dfs(grid,i-1,j);
        dfs(grid,i,j+1);
        dfs(grid,i,j-1);
    }
}
